Method and device in the dryer section of a paper/board machine

Abstract

The invention concerns a method and a device in the dryer section of a paper/board machine. In the dryer section a normal single-wire draw is applied at least partly, in which method the web (W) is passed through the dryer group on support of a drying wire (H). The drying wire (H) presses the web (W) on the drying cylinders (K n , K n+1 . . . ) against the heated cylinder faces, and on the reversing cylinders or rolls (S n , S n+1 . . . ) between the drying cylinders ( 10 ) the web (W) remains at the side of the outside curve. There is one integrated device, through which a support suction and/or blowing is produced in order to improve the runability of the web (W) and to keep the web (W) in contact with the face of the wire, and through which same device, additionally, impingement blowing is produced in order to dry the web (W) and/or to control its tendency of curling.

What is claimed is:  
     
       1. A method in a dryer section of a paper machine, in which dryer section a normal single-wire draw is applied at least partly, in which method the web (W) is passed through the dryer group on support of a drying sire ( 17 ;H), whose permeability to a drying medium is in the range between 2000-20000 m 3 /h/m 2  (cubic meters per hour per square metre), which drying wire ( 17 ;H) presses the web (W) on the drying cylinders ( 10 ,K n ,K n+1  . . . ) against the heated cylinder faces, and in which dryer section the web (W) on the reversing cylinders or rolls ( 14 ,S n ,S n−1  , . . . ) between the drying cylinders ( 10 ), remains at the side of the outside curve, and in which dryer section there is provided: 
       an impingement blowing (P 2 ) on the adjacent drying cylinders ( 10 ,K n ,K n−1  . . . ) and  
       one of a support suction and blowing (P 1 , P 3 ) inside an intercylinder pocket space (F) defined by the adjacent drying cylinders ( 10 ,K n ,K n+1  . . . ) and the reversing cylinder or roll ( 14 ,S n , S n−1  . . . ),  
       wherein  
       the suction and blowing (P 1 , P 2 , P 3 ) are accomplished by one integrated impingement drying and runnability unit (R, 20 ) extending from the intercylinder pocket (F) onto at least one drying cylinder ( 10 ,K n ,K n−1  . . . ), through which impingement drying and runnability unit is produced:  
       a suction effect by means of one of the blowing and support suction (P 1 , P 3 ) through the drying wire ( 17 ;H) to the web (W) in order to improve the runnability of the web (W) and to keep the web (W) on the face of the wire and the impingement blowing (P 2 ) through the drying wire ( 17 ;H) to the web (W) in order to dry the web (W), regulate a curling of the web (W) and to control a tendency of curling of the web (W).  
     
     
       2. A method as claimed in  claim 1 , wherein the same medium that is used as drying medium for the web (W) in impingement drying is used for controlling the runnability of the web. 
     
     
       3. A method as claimed in  claim 1 , wherein heating medium is passed as a curtain jet to one of the inlet side and outlet side of the pocket space (F), and said heating medium is passed as an ejection jet to one of the inlet and outlet side of the pocket space (F), onto a straight web that runs onto the face of a grooved perforated reversing roll (S n ,S n+1  . . . ). 
     
     
       4. A method as claimed in  claim 1 , wherein carriage of the impingement drying medium along with the wire ( 17 ) into the pocket space (F) is prevented by means of a blowing arranged in connection with the runnability unit ( 225 ), blown out of the nozzle opening ( 232 ), and directed by means of the air guide ( 231 ). 
     
     
       5. A method as claimed in  claim 1 , wherein in the method, a block ( 20 B 1 ) that communicates with a source of vacuum is employed at the outlet edge of the impingement drying unit ( 20 B) in order to produce a vacuum in the area of the outlet edge of the impingement drying unit ( 20 B). 
     
     
       6. A method as claimed in  claim 1 , wherein a blower ( 220 ) is employed in order to produce one of vacuums and pressures in connection with the impingement drying unit ( 20 A, 20 B) in connection with the runnability unit ( 20 D). 
     
     
       7. A device in the dryer section of a paper machine, which dryer section is at least partly accomplished by means of dryer groups with normal single-wire draw, in which dryer groups the web (W) is fitted to be passed through the dryer group on support of a drying wire ( 17 ;H), whose permeability to a drying medium is in the range between 2000-20000 m 3 /h/m 2  (cubic meters per hour per square metre), and in which dryer groups there are drying cylinders ( 10 ;K n ,K n−1  . . . ) against whose heated cylinder faces the web (W) is fitted to be pressed by means of the drying wire ( 17 ,H), and in which dryer groups, on the reversing cylinders or rolls ( 14 ;S n ,S n+1  . . . ) between the dryer cylinders ( 10 ), the web (W) is placed at the side of the outside curve, and which dryer section is provided with: 
       an impingement drying means extending at least onto one of the adjacent drying cylinders ( 10 , K n ,K n−1  . . . ) and  
       one of support and support suction means locating inside an intercylinder pocket space (F) defined by the adjacent drying cylinders ( 10 , K n ,K n+1  . . . ) and the reversing cylinder or roll ( 14 ; S n , S n+1  . . . ), wherein  
       in the dryer groups, from the intercylinder pocket space (F) onto at least one drying cylinder ( 10 ,K n ,K n+1  . . . ) extends one integrated impingement drying and runnability unit (R, 20 ), through which:  
       a suction effect by means of one of the blowing and support suction (P 1 , P 3 ) is applied to the web through the drying wire ( 17 ;H) in order to improve the runnability of the web, and  
       the impingement blowing (P 2 ) is applied into connection with the web (W) through the drying wire ( 17 ;H) in order to dry the paper web (W).  
     
     
       8. A device as claimed in  claim 7 , wherein from the interior of the hood (R), additionally an air jet (P 1 ) is passed to the inlet side of the pocket space (F) to produce a preventive jet so that air cannot pass into the pocket space (F), and a second air jet (P 2 ) is passed at the outlet side of the pocket space (F) to constitute an ejection jet so as to remove air out of the pocket space (F), in which case said jet is preferably directed as parallel to the running direction of the wire, in which case it operates both as a jet that removes air in evacuation of air out of the pocket space (F) and as a jet that produces a vacuum between the hood (R) and the wire (H), in which connection the vacuum is transferred through the wire (H), and the web (W) adheres, by means of the vacuum thus produced, to the wire face, and the running of the web (W) is stabilized. 
     
     
       9. A device as claimed in  claim 7 , wherein in connection with the drying cylinder (K n ) and with the subsequent suction roll (S n ) and with the subsequent drying cylinder (K n+1 ), the device comprises impingement drying units and runnability units ( 116 , 117 , 118 ;  119 , 120 , 121 ), whose hood (R) extends into connection with both of the drying cylinders (K n ,K n+1 ) and, further, into the pocket space (F) placed between the drying cylinders (K n ,K n−1 ), in which connection the air that has been passed into the interior of the frame (R) is passed as impingement drying air into connection with both of the drying cylinders (K n ,K n+1 ) and further as one of a seal and curtain jets to prevent any flow of air into the pocket space (F), in which case a jet that prevents a flow of air into the pocket space is placed at one of the inlet side and outlet side of the pocket space. 
     
     
       10. A device as claimed in  claim 7 , wherein in their connection, the drying cylinders (K n ,K n−1 ) comprise a hood (R), which extends into the pocket space (F), and that out of the hood (R) there s a flow opening (m 30 ) a flow gap, through which air is made to flow into the passage ( 80 ) between the curved frame face (R′) of the hood (R) and the drying cylinders (K n ,K n−1 ) and as impingement drying air into connection with the web (W). 
     
     
       11. A device as claimed in  claim 10 , wherein the device comprises a hood (R) into whose interior heating medium is introduced so that a part of the air is passed through the curved perforated face (Ra) placed in connection with the drying cylinder (K n ) at the outlet side of the pocket space (F) through the wire (H) into connection with the web (W) to constitute impingement drying air, and that a part of the air that has been introduced into the interior of the hood is passed into the hood (R) portion (R″) extending into the pocket space (F) and further as a jet at one of the inlet side and outlet side of the pocket space (F) into the gap between the hood (R) and the wire (H) face to prevent a leakage flow of air into the pocket space (F). 
     
     
       12. A device as claimed in  claim 7 , wherein into the pocket space (F) a blow box ( 20 ) has been fitted, by whose means an ejection blowing (P 1 ) is fitted to be produced onto the straight runs between the drying cylinders ( 10 ) and the reversing cylinders or rolls ( 14 ) in order to improve the runnability at the inlet side, and that, by means of said blow box ( 20 ), blowings (P 2 ) that dry the paper web (W) at the outlet side are fitted to be produced, which blowing (P 2 ) are fitted to be blown towards the web (W) through the wire ( 17 ). 
     
     
       13. A device as claimed in  claim 12 , wherein the blow box ( 20 ) that forms the device comprises an additional nozzle at the outlet side in order to produce a runnability and drying blowing (P 3 ) to be blown in the running direction of the web (W). 
     
     
       14. A device as claimed in  claim 12 , wherein the side wall ( 26 ) of the blow box ( 20 ) at the outlet side follows the face of the adjacent cylinder ( 10 ) at the distance of the necessary safety clearance. 
     
     
       15. A device as claimed in  claim 12 , wherein there is an ejection nozzle at the inlet side of the blow box ( 20 ). 
     
     
       16. A device as claimed in  claim 12 , wherein the nozzles of the blow box ( 20 ) at the outlet side are direct-blow nozzles. 
     
     
       17. A device as claimed in  claim 7 , wherein in connection with the runnability unit, a nozzle blowing has been arranged in order to prevent carriage of the impingement drying medium along with the wire ( 17 ) into the pocket space. 
     
     
       18. A device as claimed in  claim 17 , wherein the wall of the runnability unit ( 225 ) at the inlet side of the web (W) is corrugated and communicates with a suction chamber ( 24 ) through suction openings. 
     
     
       19. A device as claimed in  claim 7 , wherein in connection with the impingement drying unit ( 20 A, 20 B), at its outlet edge, there is a block ( 20 B 1 ), which communicates with a source of vacuum. 
     
     
       20. A device as claimed in  claim 7 , wherein in connection with the device, a blower ( 220 ) has been fitted in order to produce one of the necessary vacuums and pressures. 
     
     
       21. A device as claimed in  claim 7 , wherein the device comprises a blower ( 220 ) for producing the vacuum necessary in the device, which blower is connected with a heat exchanger to pass the air that has been sucked through the heat exchanger, and to pass the air back into the impingement drying units.